Method for reduced cycle times in multi-pass welding while providing an inert atmosphere to the welding zone

ABSTRACT

This disclosure describes a method and apparatus for controlling the temperature of a welding zone for welding together pipe sections. The temperature is controlled by a flow of inert gas through the pipes. The inert gas flow is cooled and acts as a heat sink to remove heat from the weld zone thereby controlling the weld zone temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/970,171, filed Dec. 16, 2010, herein incorporated byreference in its entirety for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

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INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject matter of this disclosure relates to the electrical heatingof metal cylinders to form a seam bond and applying a means of coolingto the metal cylinders corresponding at least in part to U.S.Classification 261/61.7 and IPC8 B23K9/02.

2. Description of Related Art

Industrial pipe systems involve multiple pipe configurations, differentdiameters and pipe wall thicknesses often joined to one of numerousconnection elements such as flanges, elbows, T junctions. Engineersdraft spool drawings as representations of a pipe section that needs tobe created. These drawings detail the angles, fitting sizes, and otherspecifications needed to create the desired pipe structures (fabricatedpieces). The pipe assembly process generally begins with preparing thesegments. Bevels are created on the pipe ends to lay down the multipleweld passes, and other pipe end or surface preparations are performed.Next the spool components are generally tack welded together to alignthe pipe sections for multi-pass welding.

Multi-pass welding is traditionally performed manually by specializedand highly skilled welders. However, various forms of automation exist.A common automation is flat-position groove welding. In flat-positiongroove welding, two or more pipe sections are set horizontally on asupport structure. The support structure rotates the pipes for welding.A fixed welding torch is aligned with the pipe junction and the pipessections are welded together while the pipes are rotating. Automatedwelding can include a fixed or stationary pipe, with the automatedwelding torch rotating around the pipe as it welds. Other forms ofsemi-automation include manual weld first passes with orbital GTAW ororbital FCAW for subsequent weld passes. Finally, multi-pass welding maybe performed by robotic arms programmed to apply welds according to thespecifications of the spools.

It is common that welding codes and or procedures limit the process to amaximum interpass temperature during the entire multi pass weld. Theprocess of multi-pass arc welding generally involves the steps of a)creating a first weld seal (root pass) of two sections of pipe, b)allowing the weld to cool, c) performing a subsequent weld over theprevious weld, and d) repeating steps b) and c) until the pipingsections are fully welded together across the thickness of the pipewall, including weld reinforcement. Many codes or weld proceduresrequire the weld area on the inside of the pipe to be free fromatmospheric contaminants such as oxygen and sometimes nitrogen. In orderto accomplish this, dams are inserted into the two sections of pipewhile performing welding. These dams form a contained interior volume ofpiping with the weld seam generally in the center. In manycircumstances, both water and oxygen should be minimized or eliminatedwhile the weld is being made and during the post welding cool downperiod. Consequently, during arc welding of thick walled pipe sectionstogether, an inert gas is continually flushed through the containedinterior volume to prevent oxidation of the weld site and to evaporateand remove moisture from the weld site.

A major materials issue with multi-pass welding of pipes is thestructural integrality of the resulting weld. It is critical in e.g.nuclear reactors, that pipes handling reactor coolant not fail due torupture. A stress fracture of key pipes in a refinery could result incatastrophic failure causing great damage and endangering many lives. Itis thus essential that these welded structures adequately withstand theextreme conditions to which they are exposed.

A variety of standards exist which quantify various materialrequirements for multi-pass welded pipes. See, e.g., Process Piping: TheComplete Guide to ASME B31.3. Third Edition. Charles Becht IV. ASMEPress, Three Park Avenue, New York, N.Y. 10016-5990. 2009; ISBN-13:978-0-7918-0286-1. A key control parameter in producing multi-passwelded pipes is the “interpass temperature” parameter. There areempirically defined minimum and maximum interpass temperatures dependingon such factors as the type of metal alloy making up the pipe sections.These temperatures define welding process conditions that produce pipewelds with acceptable material properties. In particular, before asubsequent welding pass, the weld site temperature should be at or belowthe maximum interpass temperature. In practice this requires waiting forthe prior weld's temperature to drop to at least the interpass maximumtemperature. The interval time between weld passes in the currentpractice will vary according to wall thickness and maximum interpasstemperature but can range from a few minutes to an hour or more. Thisslows down the welding process and causes undesirable idle time forhighly skilled specialty welders. There is also an ongoing risk ofoverheating the weld zone thereby causing structural flaws in the pipingproduced. A severe example of such structural flaws from overheating ofa metal during welding is warping and distortion of the physical shapeof the material.

It is therefore desirable to effect control over the temperature of weldsites in multi-pass welding to reduce or eliminate the down time betweenwelding passes. The art has not effectively addressed this problem.Solutions to interpass temperature control generally relate toaccelerated cooling between passes. These prior art operate byapplication of air and/or water for convective heat transfer from theweld. Use of air exposes the weld to oxygen and is thus contraindicatedfor the pipe welding of this disclosure. Water cooling potentially maybe used, but this requires specially adapted equipment. Exposing waterto the weld site during weld processing is also undesirable because thewater has to be removed after welding, the water can pose safety hazardsincluding electrical and slip and fall, this can also lead to oxidationon the inside of the pipe.

U.S. Pat. No. 4,152,568 describes a process of coolant circulationwithin a pipe to accelerate the cooling rate of welds. The coolant iswater, liquid nitrogen or dry ice. Liquid nitrogen is preferred forcooling from the maximum interpass temperature to 800 degrees C. U.S.Pat. No. 4,152,568 does not address multi-pass welding where three ormore welds are applied in series. U.S. Pat. No. 4,152,568 does notdescribe the control of the maximum temperature reached by the weldsite. Finally, U.S. Pat. No. 4,152,568 still requires specially adaptedequipment to carry out the described accelerated interpass coolingmethod. This method does not address the potential for metallurgicalchanges in the base material as a result of deep cryogenic treatment ofthe weld zone and other areas where the liquid nitrogen comes in contactwith the pipe. This cryogenic treatment can be advantageous byincreasing wear resistance in some materials but may also bedisadvantageous to some materials by possibly decreasing tensilestrength and or other mechanical properties. The limitations and effectsare currently being researched.

BRIEF SUMMARY OF THE INVENTION

1. A process for welding pipe sections (19) together, the processcomprising the steps of:

-   -   a) creating a first weld between the pipe sections (19) at a        weld zone (70) while using an inert purge gas comprising        nitrogen, argon, and/or helium at ambient temperatures,    -   b) establishing an flow of an inert cooled gas through an        interior (50) of the pipe sections (19) and in thermal        communication with the first weld, the inert cooled gas        comprising nitrogen, argon, and/or helium,    -   c) monitoring a temperature of the weld zone (70),    -   d) creating an additional weld between the pipe sections (19) at        the weld zone (70),    -   e) in response to the temperature of the weld zone (70) during        step d), adjusting the temperature (12, 40) and/or a flow rate        (8, 15) of the flow of the inert gas to maintain the weld        junction temperature at or below a maximum interpass temperature        during step d).

2. A process for welding pipe sections together, the process comprisingthe steps of:

-   -   a) establishing an initial flow of an ambient temperature inert        gas through an interior (50) of the pipe sections (19) and in        thermal communication with the weld zone (70),    -   b) creating a first weld at a weld zone (70) between the pipe        sections (20),    -   c) switching from ambient temperature inert gas to cooled gas        (8, 15) for remaining weld passes,    -   d) creating an additional weld between the pipe sections at the        weld zone (70),    -   e) adjusting the temperature (12, 40) and/or a flow rate of the        flow of the inert gas (8,15) to reduce the maximum temperature        reached during step c) at the weld zone (70).

3. The process of sentence 1 or 2, further comprising the step ofadjusting the temperature (12, 40) and/or the flow rate (8, 15) of theinert gas flow to a degree sufficient to accelerate the cooling rate ofthe weld after the additional weld is completed, measured relative tothe rate of cooling using an inert gas flow at ambient temperature at aninitial flow rate.

4. The process of sentence 1, wherein the maximum interpass temperatureis from 100 degrees C. to 175 degrees C. for Austenitic stainless steelsand from 250 degrees C. to 315 degrees C. for various grades of carbonsteels.

5. The process of sentence 1, 2, 3 or 4, wherein the temperature of theflow of inert gas is from −75 degrees C. to −226 degrees C.

6. The process of sentence 1, 2, 3, 4 or 5, wherein a flow rate of theflow of inert gas is from 10 scfh to 100 scfh.

7. The process of any one of sentences 1-6, further comprising the stepof establishing a flow of an inert cooled gas onto an exterior side (20,21, 80) of the weld zone (70) of the pipe sections (19) and in thermalcommunication with the weld zone (70), the inert cooled gas comprisingnitrogen, argon, and/or helium.

8. The process of any one of sentences 1-7, wherein the step ofestablishing an flow of an inert cooled gas through an interiorcomprised a sub-steps of:

-   -   i) blending cooled and ambient temperature inert gas (8, 15),        and    -   ii) measuring the temperature of the blended inert gas (12).

9. The process of any one of sentences 1-8 wherein the pipe sections arelocated on a ground outside, on a floor of a building, or are in placeat the location where the finished pipe is intended to be used.

10. An apparatus specifically adapted and configured to carry out theprocess of any one of sentences 1-9.

11. A pipe produced by the process of any one of sentences 1-9.

12. An apparatus for controlling interpass weld temperatures during amulti-pass welding operation, the apparatus comprising,

-   -   a) a containment barrier (18) adapted to at least partially        isolate an interior volume (50) of the two or more pipe sections        (19), wherein the interior volume (50) includes a part of a weld        zone (70),    -   b) an inert gas delivery sub-apparatus comprising,        -   i) an inlet (90) fluidly connected to the volume (50) and            fluidly connected to an inert gas delivery line (2, 22),        -   ii) the inert gas delivery line (2, 22) further fluidly            connected to a source of inert gas (30),        -   iii) an inert gas flow control device (8, 15) configured to            control the flow of inert gas from the inert gas source (30)            into the interior volume (50),    -   c) a temperature control device (12, 40) configured to be        capable of adjusting the temperature of an inert gas at one or        more places in the inert gas delivery sub-apparatus.

13. The apparatus of sentence 12, wherein a) the source of inert gas(30) comprises a pressurized tank comprising a liquefied inert gas stock(23) and b) the temperature control device comprises a liquefied gasvaporizer (12), the vaporizer being

-   -   a) in fluid communication with the inert gas source (30) and the        inert gas delivery line (2, 22),    -   b) configured to receive the liquefied inert gas stock (23), and    -   c) configured to vaporize the liquefied inert gas into a gaseous        state.

14. The apparatus of sentence 12, wherein a) the source of inert gas(30) comprises a pressurized tank comprising a gaseous inert gas stockand b) the temperature control device comprises a cooling coil (40) atleast partially submerged, including completely submerged, in a volumeof a liquid cryogen (23).

15. The apparatus of sentences 12, 13 or 14, further comprising atemperature probe (60) configured to be capable of measuring thetemperature of a weld junction a) between welding passes, b) duringwelding, or c) both.

16. The apparatus of sentence 12, 13, 14 or 15 further comprising acomputer in operable communication with one or more component of theapparatus, the computer specifically programmed to operate the componentin response to one or more of:

-   -   a) an instruction from an operator,    -   b) a value derived from a temperature probe (60) and/or an        inline temperature sensor.

17. The apparatus of sentence 12, 13, 14, 15 or 16 further comprising asupport scaffold adapted to position two or more pipe sections (19) inan alignment suitable for welding the pipe sections (19) together.

18. An apparatus for controlling interpass weld temperatures during amulti-pass welding operation, the apparatus comprising,

-   -   a) a means for positioning two or more pipe sections in an        alignment suitable for welding the pipe sections together (19),    -   b) a means for at least partially isolating an interior volume        of the two or more pipe sections (50), wherein the interior        volume includes a weld zone (70),    -   c) a means for providing a flow of inert gas through the        interior volume (2, 8, 18, 22), and    -   d) a means for adjusting the temperature of the flow of the        inert gas (12, 40).

19. The apparatus of sentence 18 further comprising means for measuringthe temperature (60) of a weld zone (70) a) between welding passes, b)during welding, or c) both.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 shows an exemplary apparatus and method of implementing theinvention using the same.

DETAILED DESCRIPTION OF THE INVENTION

Regardless of the general process of multi-pass welding, interpasstemperature values should be constrained to produce welds with therequired physical properties, and in some cases, the weld area must befree from oxygen and sometimes nitrogen as well. The devices and methodsdescribed herein provide a readily adopted way of controlling interpasstemperatures in a multi-weld process while at the same time, providingan inert atmosphere in the weld area. The inert atmosphere will be freefrom oxygen and/or nitrogen depending on the cooling medium chosen.While some codes or weld procedure specifications will allow the use ofnitrogen as the inerting gas, some companies or quality administratorssimply prefer the use of a completely inert gas such as argon as it canprovide a cleaner, more aesthetically pleasing surface on the weld rootpass and heat affected zone.

An exemplary apparatus for controlling interpass weld temperaturesduring a multi-pass welding operation includes a) a support scaffold b)a containment barrier, c) an inert gas delivery sub-apparatus and d) atemperature control device.

Support Scaffold

The support scaffold, vice, jack stand or other similar device holds thepipe sections in alignment with each other and/or the welding torch. Forexample, flat-position groove welding generally uses rollers to bothsupport and rotate the pipe sections. Other fabrication pieces have tobe welded in place and can not be rotated. On site assembly offabrication pieces in particular is often done manually on stationaryfabrication pieces to form the pipe structure where the pipe will beused. The support scaffold in this context may be the same structuresthat will hold the final pipe in place in the final structure.Alternatively, the pipe sections may be placed on the floor or theground outside and manually welded.

Containment Barrier

There are various types and designs of “purge dams” or containmentbarriers readily available in the market to date, or often the purgedams are made on site by the welders or fitters using one or more of thefollowing or a combination of the following; tape or purge tape,cardboard, paper, wood, purge paper etc. The containments barrier formsan isolated interior pipe volume. This interior pipe volume is thenflushed with an inert gas during welding. One form of containmentbarrier uses compression fittings to seal a hose to the end of a pipesection being welded. The hose transmits an inert purge gas from aninert gas source to the interior space of the pipes sections includingthe weld area. When welding larger diameter tubes, it is common to sealthe hose to the tube using tape. A number of other means for forming acontainments barrier are known in the art such as those disclosed inU.S. Pat. No. 4,723,064, which is incorporated herein by reference.

Inert Gas Delivery Sub-System

The Inert Gas Delivery Sub-system generally has at least three distinctelements, a source of inert gas, an inert gas delivery line (e.g. apurge hose) and an inert gas outlet.

Inert Gas Source

The source of inert gas may be any device, container or generationsource of an inert gas. Examples include air separation units andindustrial gas production facilities. The source of inert gas ispreferably a pressurized tank holding liquefied inert gas stock such asliquid nitrogen, liquid argon, or liquid helium. The cylinder can be astandard liquid cylinder, or a liquid cylinder modified with sub-coolingcoils installed. In many welding processes, the welding torch issupplied with an inert gas from an inert welding gas source. This sameinert welding gas source may be used for the temperature control processdescribed herein. In relation to industrial pipe welding for example, acommon welding process used is GTAW (Tig). The GTAW process requires asupply of gaseous argon to the actual welding torch. The same argonsource could be simultaneously used as a coolant gas for the processdescribed herein.

Inert Gas Delivery Line

Each liquid cylinder generally has a gas use outlet or connection, aliquid use outlet or connection, a gas vent valve, and pressure reliefdevices. The liquid use line connects to the inlet side of thetemperature control device, and then one end of a hose is connected tothe outlet side of the temperature control device while the other end ofthe hose is connected to the inlet purge dam. This supplies gaseousnitrogen, argon, or helium that can range in temperature from ambient(e.g. 25 degrees C.) to −75 degrees C. to −156 degrees C. to −179degrees C. (and any temperature sub-range or specific temperature withinthe forgoing range) when using either nitrogen or argon, and as cold as−212 to −226 degrees C. when using liquid helium. The inert gas deliveryline structure depends in part on the inert gas source and the specificcontext of the welding work site. The structure may include fixed inertgas delivery pipes from industrial gas production facilities and/orstandard liquefied gas dispensing hoses.

Temperature Control Device

The temperature control device may be any device capable of modifyingthe temperature of the inert liquid forming the inert gas flow throughthe contained interior volume of pipe sections. One preferred componentof the temperature control device when the inert gas is derived from aliquefied gas stock is a electric heater or vaporizer attached to theliquid supply connection of a cylinder of liquid nitrogen, argon, orhelium. These devices are available on the market. The vaporizer may bein fluid communication with the inert gas source and the inert gasdelivery line such that the vaporizer receives the liquefied inert gasstock and vaporizes the liquefied inert gas into a gaseous state.

Another component of the temperature control device in embodiments usinga liquefied inert gas stock may be a cooling coil completely or at leastpartially submerged in a liquefied inert gas stock. A stream of gaseousnitrogen, argon, or helium is circulated through the submersed coil toproduce a sub cooled gas, and then flows through the vaporizer or heaterto control the temperature to the desired range, and then is supplied tothe inside of the piping fabrication piece via the purge dams.

An apparatus suitable for practicing the invention herein may include anumber of other components including a temperature probe to provide acontinuous monitoring of the temperature of the base material at theweld zone. A temperature probe may also be inserted into the inside ofthe pipe to monitor the inside temperature.

Temperature Probe

Temperature probes are typically electric and are readily available inthe market. Suitable infrared thermometers are also commerciallyavailable.

Automated Temperature Control

The temperature probe and temperature control device for the inert gasmay be linked by a computer specifically programmed to respond to thetemperature from the probe to adjust the temperature and/or flow rate ofthe gas to control the temperature of the weld zone.

EXAMPLE

Standard gas cylinder 30 supplies the initial ambient temperature inertgas for creating a first pass weld between the pipe sections 19 via gasdelivery lines 2 and 22. This same gas cylinder is then switched byvalve connections 15 and 8 to temperature control device 40. In eithercase (ambient or cooled), the inert gas flows through gas delivery lines2 and 22 through containment dams 18 and into the internal space 50 ofpipe sections 19. Temperature probe 60 is a laser, non-contact infraredthermometer. The temperature probe 60 is used to monitor the temperatureof the weld zone 70.

After the initial weld using ambient temperature inert gas, the switchvalve connections 15 and 8 are actuated manually to deliver inert gasvia the temperature control device 40. The switch valve 15 may haveintermediate settings whereby ambient temperature gas flows through bothbypass gas delivery line 17 and temperature control device 40. The flowsof ambient and cooled gas may optionally be blended by a mechanicalmixer inline with gas delivery line 50. A separate temperature sensormay optionally be in communication with the gas in line 2 to measure thetemperature of the inert gas being sent to the pipe sections 19. Theinert cooled gas may optionally also be delivered to the exterior 80 ofthe pipe sections 19 at the weld zone 70 via external line 21. Theexternal gas line may be connected to a collar 20 placed around the weldzone 70 for delivery to the weld zone 70.

The temperature control device 40 is configured to receive the inert gas(including but not limited to nitrogen) from cylinder 30 and adapted todecrease or control the temperature of the inert gas for delivery viagas delivery line 2 to the weld zone 70. In this example, thetemperature control device comprises the following components:

-   1. Outer vessel burst disc-   2. Ambient, Cooled, or Sub-Cooled gaseous Argon, Nitrogen, or Helium    outlet to process-   3. Liquid fill/withdraw line-   4. Inner Vessel Rupture disc-   5. Pressure Gauge-   6. Relief valve-   7. Vent line-   8. Gaseous Nitrogen, Argon, or Helium inlet—to be cooled    (Alternative Method-Optional)-   9. Outer vessel-   10. Inner vessel—containing liquid Nitrogen, Argon, Helium, or CO2-   11. Floating liquid level gauge-   12. In-line gas Heater/Vaporizer-temperature control device-   13. Relief valve-   14. Pressure Gauge-   15. Manual or Automated Valve or Solenoid-   16. By-pass to permit use of liquid argon, nitrogen, or helium    contained in the cylinder, without using the sub-cooling coils-   17. By-pass to permit the use of ambient temperature Nitrogen,    Argon, or Helium for making initial or root pass.-   18. Purge Dam-   19. Fabrication Piece Example-   20. External Application Device (Alternative Method-Optional)-   21. Supply Line for External Application (Optional)-   22. Supply Line for Internal Application-   23. Liquid Nitrogen, Argon, or Helium-   24. Pressure Regulator

The method of cooling the inert gas in this example is to flow theambient temperature inert gas through a cooling coil 40. The coolingcoil 40 is submerged in a cryogenic liquid such as liquid nitrogen. Inthis example, final cooled inert gas temperature may be adjusted toanywhere between ambient temperature and the temperature and −212degrees Celsius by blending cooled inert gas with ambient temperatureinert gas (optionally through a static mixer with temperature determinedby an inline temperature sensor).

An alternative embodiment used liquid cryogen and a heated vaporizer todeliver an inert gas at a specified temperature. In other alternativeembodiments, the delivery pressure of the inert gas may be regulated byone of more inline pumps to control the flow rate of the inert gas inaddition to the flow valves (e.g. valve 15) and the pressure derivedfrom the inert gas source (e.g. standard cylinder 30).

One or more of the temperature probe 60, inline temperature sensor, flowvalves 15, optional inert gas pressurizing pump may be operated by thewelder via a computer operably connected with devices for operatingthese components. For example, valves 15 and 8 may have a motorconfigured to switch the valves to different positions. The computer maybe specifically programmed to automate one or more steps of the process.For example, the ratio of ambient and cooled inert gas may be adjustedin response to temperature probe 60 to decrease the temperature of theinert gas if the weld zone 70 reaches a predetermined thresholdtemperature. The computer may further operate the vaporizer 12 to adjustthe temperature of the inert gas flowing to delivery line 2.

The invention claimed is:
 1. An apparatus for controlling interpass weldtemperatures during a multi-pass welding operation, the apparatuscomprising: a) a support scaffold configured to position two or morepipe sections in an alignment suitable for welding the pipe sectionstogether; b) a containment barrier configured to at least partiallyisolate an interior volume of the two or more pipe sections, wherein theinterior volume includes a part of a weld zone; c) an inert gas deliverysub-apparatus comprising, i) an inlet fluidly connected to the interiorvolume and fluidly connected to an inert gas delivery line, ii) theinert gas delivery line further fluidly connected to a source of inertgas, iii) an inert gas flow control device configured to control theflow of inert gas from the inert gas source into the interior volume,and iv) a vessel having an outer vessel and an inner vessel wherein theinner vessel is configured to hold a volume of cryogenic fluid; and d) atemperature control device comprising a cooling line at least partiallydisposed within the inner vessel, wherein the cooling lines is in fluidcommunication with the source of inert gas and the inert gas deliverylane, wherein the temperature control device is configured to adjusttemperature of the flow of inert gas to a temperature between −226° C.and −156° C., when the cooling line is at least partially submerged inthe volume of cryogenic fluid.
 2. The apparatus of claim 1, wherein thesource of inert gas comprises a pressurized tank comprising a liquefiedinert gas stock and the temperature control device comprises a liquefiedgas vaporizer, the vaporizer being in fluid communication with the inertgas source and the inert gas delivery line, configured to receive theliquefied inert gas stock, and configured to vaporize the liquefiedinert gas into a gaseous state.
 3. The apparatus of claim 1, wherein thesource of inert gas comprises a pressurized tank comprising a gaseousinert gas stock and the cooling line comprises a cooling coil at leastpartial submerged in a volume of a liquid cryogen.
 4. The apparatus ofclaim 1, further comprising a temperature probe configured to measurethe temperature of a weld junction between welding passes, duringwelding, or both.
 5. The apparatus of claim 1, further comprising acomputer in operable communication with one or more component of theapparatus, the computer specifically programmed to operate the componentin response to one or more of an instruction from an operator, a valuederived from a temperature probe and/or an inline temperature sensor. 6.An apparatus for controlling interpass weld temperatures during amulti-pass welding operation, the apparatus comprising a) a means forpositioning two or more pipe sections in an alignment suitable forwelding the pipe sections together; b) a means for at least partiallyisolating an interior volume of the two or more pipe sections, whereinthe interior volume includes a weld zone; c) a means for providing aflow of inert gas through the interior volume; and d) a means foradjusting the temperature of the flow of the inert gas to a temperaturebetween −226° C. and −156° C., wherein the means for adjusting thetemperature comprise a temperature control device comprising a coolingline at least partially disposed within a vessel, wherein the vessel isconfigured to hold a volume of cryogenic fluid.
 7. The apparatus ofclaim 6 further comprising means for measuring the temperature of a weldzone between welding passes, during welding, or both.